1. Field of the Invention
The present invention relates to a disc reproducing apparatus, such as a disc player, and a method of operating the same, and more particularly relates to a disc reproducing apparatus preferred for use in reproduction of a CD-ROM utilized as a storage medium for storing data and programs.
2. Description of the Related Art
In a conventional CD-ROM player, the rotation speed of a CD-ROM disc has been controlled at a target rotational speed of the spindle servo control system set to a frequency of 7.35 kHz of the frame synchronization signal or a whole multiple of the same.
Further, it becomes possible to read the data from the disc after the traverse only after the spindle rotational speed approaches the target value and enters into the capture range of the PLL (Phase Locked Loop) circuit. Therefore, a certain degree of time is necessary from the time when an optical pick-up (hereinafter simply referred to as a pick-up) reaches the read position of the next data to the time when it becomes possible to read the data. Thus, the seek time is considerably and undesirable prolonged.
More specifically, the line speed Va at a first position A becomes Ra/Rb times the line speed Vb at a second position B, where the radius at the position A and the line speed before the traverse of the pick-up are Ra and Va, respectively and the radius at the position B and the line speed after the traverse of the pick-up are Rb and Vb, respectively. On the other hand, the ratio of radius of the position A and position B reaches a maximum in a case where the position A is on the innermost circumference and the position B is on the outermost circumference. This ratio is about 2.52 for a standard sized disc. For example, in a case where an 8 times speed reproduction (which is 8 times the speed of a normal reproduction) is carried out at the innermost circumference, the pick-up is traversed to the outermost circumference for the reproduction, and the reproduction speed corresponds to 20.16 times speed at the instant of movement. Namely, there is generally a margin of safety in the reproduction speed of several tens of percent. The above reproduction speed largely exceeds the permissible range; therefore no data can be read until the line speed of the pick-up after the traverse to the outermost circumference is lowered to the maximum reproduction line speed, which leads to a considerable elongation of the seek time.